Mix the mashed potatoes, red chilly, coriander, cumin and raw mango powders, chopped coriander, 1 chopped onion and salt to taste. Make into a smooth paste. Form into equal-sized patties. Heat oil on a griddle and shallow fry these patties till crisp and golden. Drain on paper towels. Boil the roughly mashed chickpeas with the cloves, cardamom and peppercorns and salt to taste. Once done, remove the whole spices and discard. To serve the chaat, put 2 hot patties in a plate and spoon some chickpea mixture over them. Add both chutneys to taste. Sprinkle chopped onion and corainder to garnish. Sprinkle chaat masala over the whole dish.